How are your back rolls? Its all the same. If your fear of rolling prevents any front rolls, try back rolls. When you roll back and touch with your toes, push off back to where you started. It will help get your body into the right shape with out the vertical drop.
You can also kneel on the mat and (we'll pick a side now) have your left knee slightly forward. Pass your left arm passed you left knee and then right knee so you left shoulder is on the mass and your left hand is behind your right foot. Now raise up you your right foot and push off to role on you left shoulder. Again, no drop. I do caution you that this is to teach your body how to be round, but is not a good way to role since you lose the support of the arm.
Finally. Get a pilates ball and give it a hug. Now, holding the ball, roll with the arm. The ball supports the arm (almost like an unbendable arm....) so you can roll without worrying about the arm collapsing.
And in closing, I'll have to quote Paul Muadd'b: Fear is a mindkiller. Fear is the little death.